Organic electro luminescent display and method for fabricating the same

ABSTRACT

An organic electro luminescent display with auxiliary layers on a cathode contact and an encapsulating junction region to easily remove polymer organic layers of the junction and a method for fabricating the same. The organic electro luminescent display has the first electrode formed on a lower insulating substrate, a pixel defining layer formed to make some portions of the first electrode opened over the entire surface of the lower insulating substrate, an organic emission layer formed on an opening of the first electrode, the second electrode formed on the organic emission layer, an upper substrate for encapsulating the first electrode, the organic emission layer and the second electrode, and auxiliary layers formed on the cathode contact and the encapsulating junction region of the lower insulating substrate.

CLAIM OF PRIORITY

[0001] This application claims priority to an application entitled“ORGANIC ELECTRO LUMINESCENCE DISPLAY AND METHOD FOR FABRICATING THESAME”, filed in the Korean Intellectual Property Office on 10 Jun. 2003and assigned Serial No. 2003-37244, and filed on 23 Jun. 2003 andassigned Serial No. 2003-40808, and filed on 2 Sep. 2003 and assignedSerial No. 2003-61163, the contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to an organic electro luminescent displayand a method for fabricating the same and, more particularly, to anorganic electro luminescent display having an auxiliary layerencapsulating junction region and a method for fabricating the same.

[0004] 2. Description of the Related Art

[0005] Generally, an organic electro luminescent display is an emissivedisplay capable of emitting light by electrically exciting a fluorescentor phosphorescent organic compound, and phosphorescent organic compoundcan be driven by a low voltage and has a thin form-factor, a wideviewing angle and a fast response speed, so that the electro luminescentdisplay can solve problems that have been found in liquid crystaldisplays. Therefore, the electro luminescent display has attractedattention as a next-generation display.

[0006] Such an organic electro luminescent display has a structure thathas an organic light emitting diode (OLED) including an organic layerhaving at least emission layer(EML), an anode, and a cathode, whereinthe organic layer having a predetermined pattern is formed on a glass orother transparent insulating substrate, and the anode and cathodeelectrodes are formed on upper and lower portions of the organic layerfor applying a driving voltage to the organic layer. The organic layerconsists of organic compounds.

[0007] In the organic electro luminescent display having theabove-mentioned basic structure, as an anode electrode and a cathodeelectrode voltages are applied to the electrodes, holes injected fromthe electrode that have been applied with the anode electrode voltageare transported to the emission layer (EML) through a hole transportinglayer (HTL), and electrons are injected from the electrode that havebeen applied with the cathode electrode voltage are transported to theemission layer (EML) through an electron transporting layer (ETL). Theelectrons and holes are then recombined in the emission layer(EML) tocreate excitons, and the exitons are then changed from an exciting stateto a ground state, thereby emitting an organic substance of the emissionlayer (EML) and embodying a required image.

[0008] In the above-mentioned organic electro luminescent display, whena polymer material is used for the organic layer, the organic layer isgenerally formed on a substrate by spin coating. However, when theorganic layer is formed by the spin coating, the organic layer is alsoformed in regions other than the pixel portion. Thus, the organic layerof the encapsulating junction region needs to be removed to encapsulatean inner structure of the organic electro luminescent display.

[0009] In a prior art, a cleaning process using an organic solvent wasperformed to remove the organic layer of the encapsulating junctionregion, however, the process has a significantly low accuracy and theorganic solvent often penetrates into the pixel portion, so that thereis a high possibility of damaging the pixel portion.

[0010] To solve the above-mentioned problems, a method using a laser isdisclosed to remove a foreign substance including organic emissivematerials off a substrate. According to a Korean laid-open PatentApplication No. 2000-0036020, a method for removing the foreignsubstance using the laser is disclosed. This method removes organic orinorganic foreign substances on the substrate by directly irradiatingthe ultraviolet laser on the surface of the substrate.

[0011] In the case of the substrate of the prior art, a metal wiring anda passivation layer are usually deposited on a glass substrate in theencapsulating junction region. However, the laser energy absorption rateof the passivation layer is small so that the organic layer is noteasily removed by using a laser.

SUMMARY OF THE INVENTION

[0012] It is therefore an object of the present invention to provide foran improved design for an electro luminescent display.

[0013] It is also an object of the present invention to provide for anovel method for making an electro luminescent display.

[0014] It is further an object of the present invention to provide for anovel structure of an electro luminescent display that allows for easierselective removal of an organic emissive layer using a laser.

[0015] It is yet another object of the present invention to provide anovel method of making an electro luminescent display that moreefficiently selectively removes unwanted materials using a laser withoutdestroying other portions of the electro luminescent display.

[0016] It is further an object of the present invention to provide anovel structure for an electro luminescent display that allows forsealant to be efficiently cured by ultraviolet light while preventingother parts of the electro luminescent display from being harmed by thecuring ultraviolet light.

[0017] It is further an object of the present invention to provide anovel method for making an electro luminescent display that allows forsealant between the substrates and between the electrodes to beefficiently sealed by ultraviolet light where other portions of thedisplay are not harmed by exposure to the curing ultraviolet light.

[0018] These and other objects can be achieved by an organic electroluminescent display, which has the first electrode formed on a lowerinsulating substrate, a pixel defining layer formed to make someportions of the anode electrode opened over the entire surface of thelower insulating substrate, an organic layer formed on an opening of theanode electrode, the second electrode formed on the organic layer, anupper substrate for encapsulating the anode electrode, the organic layerand the cathode electrode, and auxiliary layers formed on a cathodecontact and an encapsulating junction region of the lower insulatingsubstrate. The organic layer is deposited over the first electrode andthe auxiliary layers. The organic layer is selectively removed by laserfrom the auxiliary layers. The material for the auxiliary layers arecarefully chosen so that the organic layers can be removed from theauxiliary layers with relatively little amount of laser light.

[0019] The present invention also includes a method for making theelectro luminescent display having the auxiliary layers and theapplication of laser light to remove the organic layers off theauxiliary layers via laser ablation.

[0020] The invention separately provides a novel structure for anorganic electro luminescent display. The novel display is made up ofupper and lower substrates bounded to each other by an ultraviolet lightcurable sealant. The sealant is placed around the pixel region in anencapsulation region. A reflecting plate is placed adjacent to thesealant. The reflecting plate is used to reflect the ultraviolet lightso that less light is needed to cure the sealant. Less light or moreefficient use of the ultraviolet light means that the other parts of theelectro luminescent display are not degraded or damaged due to exposureto an excessive amount of ultra violet light. The sealant and thereflecting plate can be used in either active or passive matrix pixelstructures. In place of the reflecting plate, a waveguide can be usedadjacent to the sealant.

[0021] The present invention also pertains to a method of making theabove structure for an electro luminescent display including theapplication of the reflective plate and/or waveguide and the ultravioletcuring step.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] A more complete appreciation of the invention, and many of theattendant advantages thereof, will be readily apparent as the samebecomes better understood by reference to the following detaileddescription when considered in conjunction with the accompanyingdrawings in which like reference symbols indicate the same or similarcomponents, wherein:

[0023]FIG. 1 is a graph illustrating empirically a relationship betweenapplication of laser energy versus removal of an organic layer absentthe use of auxiliary layers under the organic layer;

[0024]FIG. 2 is a plane view for explaining an organic electroluminescent display;

[0025]FIG. 3 is a plane view showing an organic electro luminescentdisplay according to the first three embodiments of the presentinvention;

[0026]FIGS. 4A to 4D are cross-sectional views illustrating the processof making the display of FIG. 3 according to a first embodiment of thepresent invention;

[0027]FIG. 5 is a graph illustrating empirically a relationship betweenapplication of laser energy versus removal of an organic layer when theorganic layer is formed over the auxiliary layers according to thepresent invention;

[0028]FIG. 6A is an exploded perspective view showing an organic electroluminescent display according to a fourth embodiment of the invention;

[0029]FIG. 6B is a cross-sectional view of the display of FIG. 6A takenalong the I-I′;

[0030]FIG. 7 is a view illustrating both a pixel region for an activematrix pixel and an encapsulating junction region according to thefourth embodiment of the invention;

[0031]FIG. 8 is a cross sectional view of the encapsulation junctionregion according to the fourth embodiment of the present invention wherea reflection plate is on an inside side of the lower insulatingsubstrate;

[0032]FIGS. 9 and 10 are plane views for explaining an arrangement of areflection plate vis-a-vis the sealant and the pixel region according tothe fourth embodiment of the present invention;

[0033]FIG. 11 illustrates a cross section of an encapsulation junctionregion according to a fifth embodiment of the present invention wherethe reflection plate is on an inside side of the upper substrate;

[0034]FIG. 12 illustrates a cross section of an encapsulation junctionregion according to a sixth embodiment of the present invention wherethe reflection plate is on an outside side of the lower insulatingsubstrate;

[0035]FIG. 13 illustrates a cross section of an encapsulation junctionregion according to a seventh embodiment of the present invention wherethe reflection plate is on an outside side of the upper substrate;

[0036]FIGS. 14A and 14B illustrate a cross section of an encapsulationjunction region according to an eighth embodiment of the presentinvention where a wave guide is located on an inside side of the lowerinsulating substrate;

[0037]FIGS. 15A and 15B illustrate a cross section of an encapsulationjunction region according to a ninth embodiment of the present inventionwhere a wave guide is located on an inside side of the upper substrate;and

[0038]FIGS. 16A and 16B illustrate a cross section of an encapsulationjunction region according to a tenth embodiment of the present inventionwhere there are two wave guides present, one on an inner surface of theupper substrate and another on the inner surface of the lower insulatingsubstrate.

DETAILED DESCRIPTION OF THE INVENTION

[0039] Turning now to FIG. 1, FIG. 1 illustrates empirical results forthickness of removed foreign substance based on number of laser pulsesapplied and the energy of each pulse. As illustrated in FIG. 1, as thenumber of laser pulses increases, the amount or thickness of removedforeign substances does not increase in a linear fashion with the numberof laser pulses applied. For example, as the thickness of the remainingorganic layers becomes thinner, the removal rate per additional laserpulse decreases, so that a significant amount of energy and a largenumber of laser pulses are required to completely remove the residualsubstances. Because a large number of laser pulses at a high energy perpulse is needed to completely remove the foreign substance, the lasermay cause damage to the substrate in the foreign substance removalprocess.

[0040] In addition to the removal of foreign substances by a laser, inthe organic electro luminescent display of the prior art, a sealant isused to join the substrates together. An upper substrate is bound to alower insulating substrate via this sealant. The sealant also serves toencapsulate organic electro luminescent elements and plays a role indetermining a lifetime, efficiency, etc. of the organic electroluminescent elements.

[0041] The organic electro luminescent element mainly is divided into aninner pixel portion that actually emits light and a pad portion forconnecting an external driving IC for driving the pixel portion, whereinthe driving portion and the pad portion are connected by a wiring madeof opaque metals to minimize resistance. In this case, an encapsulatingprocess using a sealant is performed to prevent moisture and air from anoutside of a display from coming into contact with and destroying theorganic electro luminescent element. The sealant is ordinarily cured byexposure to light, especially ultraviolet light. However, when the lowerinsulating substrate is attached to and encapsulated by the uppersubstrate using the ultraviolet cured sealant, it takes more time tocure the sealant using the ultraviolet light. Because an immense amountof ultraviolet light is needed to cure the sealant, the ultravioletlight can damage other portions of the display, either by heating partsup or causing an unwanted chemical reaction in the display. If theamount of ultraviolet light used to cure the sealant is reduced toprevent the damage to other parts of the display, the sealant will notbe fully cured because the sealant has not received adequate exposure tothe ultraviolet light to fully cure.

[0042] Turning now to FIG. 2, FIG. 2 illustrates an organic electroluminescent display of the prior art (FIG. 5 of Korean laid-open PatentApplication No. 2000-0036020). The process used to form the display ofFIG. 2 will now be described. A plurality of first electrodes 3 made ofoptically transmissive materials are formed in an arbitrary pattern,such as a stripe pattern, over one surface of a lower insulatingsubstrate 1. Lower insulating substrate 1 is made out of a material thatis both electrically insulating and optically transmissive. Aninsulating layer 5 is formed on the first electrodes 3, and a pluralityof second electrodes 7 are formed on insulating layer 5 in a stripepattern to a direction orthogonal to the first electrodes 3.

[0043] In this case, pixel portions of the organic electro luminescentdisplay are where the first electrodes 3 and the second electrodes 7 arecross each other. Where second electrodes 7 and first electrodes 3 crosseach other, the insulating layer 5 in these crossed regions is notpresent. Instead, a thin organic layers disposed in these cross overregions. The organic emissive material (not illustrated in FIG. 2) isalso in electrical contact with both the first electrodes 3 and thesecond electrodes 7 in the cross over areas.

[0044] In this case, an upper substrate 9 (illustrated as a dotted linein FIG. 2) is disposed over a lower substrate 1, and the lower substrate1 and the upper substrate 9 are bound to each other by a sealant that isnot illustrated in FIG. 2, so that the organic electro luminescentdisplay of FIG. 2 is formed.

[0045] According to the above-mentioned structure of FIG. 2, someportions of the first electrodes 3 and the second electrodes 7 areexposed outside the substrates 1 and 9 so that electrodes 3 and 7 can beelectrically connected to circuit driving elements, for example FPC(Flexible Printed Circuit, 11). Circuit 11 is electrically connectsexternal equipment to the organic electro luminescent display by thermalcompression, etc.

[0046] However, in the organic electro luminescent display having theabove-mentioned structure, the process of applying and curing thesealant is not properly performed when the lower substrate 1 and theupper substrate 9 are sealed together, thereby decreasing the lifetimeand reliability of the product. In the typical prior art, a sealingmaterial is applied along the periphery of the lower substrate 1 asdescribed above and the upper substrate 9 is mounted thereon, andultraviolet rays are irradiated from the rear surface of the lowersubstrate 1 and the sealing material is cured, so that the lowersubstrate 1 and the upper substrate 9 are bonded together.

[0047] When the ultraviolet rays irradiate the sealing material disposedin a portion of the display that is exposed outside the first and secondelectrodes 3 and 7 on the substrates 1 and 9 (i.e., the lower and rightsides of FIG. 2), the sealing material was cured without any significantproblems because the ultraviolet light was not blocked or hindered bythe electrode layers 3 and 7. However, when the ultraviolet raysirradiate the sealing material disposed in a portion of the displaywhere the striped patterns of electrode layers 3 and 7 are present(i.e., the upper and the left sides in FIG. 2) the presence of theelectrode layers 3 and 7 hinders the ultraviolet rays from effectivelyreaching the sealant between the substrates 1 and 9 thus requiring morepulses and/or higher energy pulses to fully cure the sealant in theseregions of the display. If the sealant is not properly cured by anadequate exposure to ultraviolet light, air and moisture will then beallowed to penetrate through the sealant and into the emissive layers tocause deterioration of a display.

[0048] The present invention has 10 embodiments. The first threeembodiments concentrate on the auxiliary layers in both structure and inmethod of making. Organic layers on top of the auxiliary layers are moreeasily removed via exposure to a laser than if the auxiliary layers werenot present.

[0049] First Embodiment

[0050] Turning now to FIG. 3, FIG. 3 is a plane view illustrating anorganic electro luminescent display according to a first embodiment ofthe present invention, and FIGS. 4A to 4D are cross-sectional viewsillustrating a process for making the organic electro luminescentdisplay of FIG. 3 according to an embodiment of the present invention.

[0051] Referring to FIG. 4A, a first electrode (or anode electrode) 1110is deposited on substrate (or lower substrate) 1100. First electrode ismade out of a transparent and conductive material such as ITO (indiumtin oxide), IZO (indium zinc oxide) or ICO (indium cesium oxide). Thistransparent first electrode material is deposited and patterned on thelower insulating substrate 100, and a transparent anode electrode, inother words, the first electrode 1110 formed in the pixel portion. Lowersubstrate 100 may be a transparent substrate made out of an electricallyinsulating material, such as glass.

[0052] In the first embodiment, the auxiliary layers 120 and 130 aremade out of the same material as the first electrode 110. Therefore, theauxiliary layers 120 and 130 are deposited and patterned on lowersubstrate 100 at the same time as when the first electrode 110 isdeposited and patterned on lower substrate 100. Auxiliary layer 120 isformed at cathode contact A while auxiliary layer 130 is formed atencapsulating junction region B.

[0053] After forming the auxiliary layer 130 on the encapsulatingjunction region B, the auxiliary layer 120 on the cathode contact A, andthe anode 110 of the pixel portion, a pixel defining layer 140 isdeposited and patterned on first electrode 110 covering parts of firstelectrode 110 and leaving other parts of the top surface of firstelectrode exposed. The pixel defining layer 140 is preferably aninorganic material and a polymer such as an acrylic photoresist or apolyimide.

[0054] Next, the organic layer 150 is deposited to cover the pixeldefining layer 140, the exposed portions of the first electrode 110, theauxiliary layers 120 and 130, and over exposed portions of lowersubstrate 100. The organic layer 150 is preferably formed by spincoating. The organic emission layer 150 preferably includes at least anemission layer(EML) and has a multi-layered structure made up of atleast one of a hole injection layer (HIL), a hole transporting layer(HTL), an emission layer(EML), an electron transporting layer (ETL), andan electron injection layer (EIL).

[0055] Referring now to FIG. 4B, after forming the organic layer 150,the organic layers on the auxiliary layers 120 and 130 over cathodecontact A and the encapsulating junction region B of the substrate areremoved. The process of selectively removing the organic layers 150 fromthe auxiliary layers 120 and 130 is preferably accomplished by exposingthese portions of organic layers 150 with light pulses from a laser.This process of removing the organic layers 150 using a laser is calledlaser ablation. In addition, a type of the laser can be selected from anUV based one (Eximer laser, Nd: YAG laser, etc) to an IR based one (Nd:YAG, CO₂ laser, etc) according to a material of a light source.

[0056] After removing the organic layers from the tops of the auxiliarylayers 120 and 130, a conductive material is then deposited andpatterned on the structure to form the second electrode or cathodeelectrode 160. The cathode electrode 160 performs a role of transportingelectrons to the electron transporting layer of organic layer 150 byusing a metal electrode such as Al, Mg, Ag, Ca that has a low workfunction.

[0057] Referring now to FIGS. 4C and 4D, after forming the cathodeelectrode 160, an upper substrate 180 is attached to the top of theelectro luminescent display using an encapsulating adhesive 170. Theencapsulating adhesive is formed over auxiliary layer 130 which is overencapsulating junction region B of lower substrate 100. Therefore,encapsulating adhesive 170 is formed around the periphery of the electroluminescent display and surrounds the pixel region.

[0058] Referring to FIG. 5, FIG. 5 is a graph illustrating empiricallythe amount of an organic layer 150 that is removed by a laser based onthe number of laser pulses and the energy intensity of each pulse. FIG.5 is for the scenario of where the organic layers 150 is supported byauxiliary layers 120 and 130. FIG. 5 is to be compared with FIG. 1 whichillustrates removal thicknesses of the organic layers when the organiclayers 150 are not on top of an auxiliary layer. In the method forremoving foreign substances on the substrate 100 where the foreignsubstances are organic layers on top of an auxiliary layer 120/130, byusing the auxiliary layers 120 and 130, the organic layers are moreeasily removed since less pulses and less intensity is needed to removethe organic layers when they are supported by auxiliary layers 120 and130. It is to be appreciated that other materials can also be removed bythe laser in addition to the organic layers. Therefore, in thisspecification, foreign substances includes the organic layers but is notlimited thereto. Less number of pulses and less intensity of pulsesmeans that the remainder of the electro luminescent display sustainsless damage from the laser pulses when auxiliary layers 120 and 130 areused (FIG. 5) compared to when they are not used (FIG. 1).

[0059]FIG. 5 illustrates that 12 pulses with an energy intensity of 75J/cm² can remove the entire organic layer if the organic layer issupported by auxiliary layers 120 and 130. This compares with 25 pulsesof 100J/cm² for when the organic layers are not supported by theauxiliary layers. Because having the auxiliary layers 120 and 130present allows for the removal of the organic layers with less pulseswith less intensity, the other parts of the electro luminescent displaysustain less damage when auxiliary layers 120 and 130 are incorporatedinto the design.

[0060] More preferably, a removing depth of the organic layer can bemaximized by irradiating the laser with energy density not less than 125mJ/cm². That is, when the organic layers are removed by using theauxiliary layer and the laser, energy required for removing the organiclayers is small.

[0061] Second Embodiment

[0062] The organic electro luminescent display according to a secondembodiment has a similar structure as that of the first embodimentexcept the material used for the auxiliary layers 120 and 130 isdifferent. In the second embodiment, the material used in the auxiliarylayers 120 and 130 is the same as the material used in pixel defininglayer 140. Therefore, pixel defining layer 140 and the auxiliary layers120 and 130 can be formed at the same time. The pixel defining layer andthe auxiliary layers are deposited at the same time and the patterningand etching of the pixel defining layer 140 and auxiliary layers 120 and130 are accomplished in a single step. As discussed previously, thepixel defining layer 140 is preferably an inorganic material and apolymer such as an acrylic photoresist or a polyimide. By having theauxiliary layers 120 and 130 made out of the same material as the pixeldefining layer 140, the number of pulses needed and the energy intensityof each pulse to remove the organic layer is reduced from the case ofFIG. 1 where no auxiliary layers were present.

[0063] Third Embodiment

[0064] The organic electro luminescent display according to a thirdembodiment has a similar structure as that of the first embodimentexcept that the auxiliary layers 120 and 130 for removing the organiclayers 150 are formed by using materials having a laser energyabsorption rate higher than that of the organic layer 150 for the laserwavelength used to remove the organic layer.

[0065] That is, after forming the pixel defining layer 140 in the firstembodiment, the auxiliary layers 120 and 130 are formed on the cathodecontact A and the encapsulating junction region B by depositing andpatterning materials having a higher laser energy absorption rate forthe laser wavelength used in the removal process

[0066] The third embodiment is not necessarily mutually exclusive fromthe first or the second embodiment. For example, use of ITO, IZO or ICOcould result in the auxiliary layer having a higher absorption of thelaser light than the organic layer and thus the auxiliary layers 120 and130 can still be made at the same time as the first electrode 110. Also,use of acrylic photoresist or polyimide for auxiliary layers 120 and 130may have a higher absorption than organic emission layer 150 and thusthe auxiliary layers 120 and 130 can be made at the same time that thepixel defining layer 140 is made.

[0067] Now embodiments 4 through 10 will now be discussed. In theseembodiments, the focus is on an ultraviolet cured sealant used to fix atop substrate to the bottom substrate. A reflecting plate and/or a waveguide is placed adjacent to the sealant so that the sealant can be curedwith less ultraviolet light than if no reflecting plate or waveguide isused. Consequently, by using less ultraviolet light to cure, theremaining parts of the electro luminescent display are subjected to lessultraviolet radiation and thus less damage results.

[0068] Fourth Embodiment

[0069] Turning now to FIGS. 6A and 6B, FIG. 6A is an explodedperspective view illustrating an organic electro luminescent displayaccording to a fourth embodiment of the invention, and FIG. 6B is across-sectional view taken along the I-I′ direction of FIG. 6A.Referring to FIGS. 6A and 6B, the organic electro luminescent display ofthe fourth embodiment of the present invention has a structure that alower insulating substrate 200 having a pixel portion is bonded to anupper substrate 320 at an encapsulating junction region, the pluralityof pixels being located in the pixel portion. That is, in the organicelectro luminescent display of the present invention, the pixel portionis formed on the upper side of the transparent lower insulatingsubstrate 200, and can be formed in a typical structure of the organicelectro luminescent display. The fourth embodiment can be either apassive matrix or an active matrix using thin film transistors or TFTs.

[0070] For example, when the organic electro luminescent display L isformed in a passive matrix (PM) type, the pixel portion is made up ofelectrode layers corresponding anode and cathode electrodes,respectively, and organic layers having emission layer disposed onpositions corresponding to the common portions where the anode andcathode layers cross each other. When the organic electro luminescentdisplay is formed in a active matrix (AM) type, the pixel portion canfurther include thin film transistors TFTs. The fourth embodiment of thepresent invention can be applied to any structure with the pixelportion, however, for example, an active matrix organic electroluminescent display will now be described in conjunction with FIG. 7.

[0071] Turning now to FIG. 7, FIG. 7 illustrates a cross-sectional viewillustrating an active matrix type pixel and an encapsulating junctionregion according to the fourth embodiment of the present invention. FIG.8 is a cross-sectional view illustrating an encapsulating junctionregion of the organic electro luminescent display according to thefourth embodiment of the invention. The organic electro luminescentdisplay according to the fourth embodiment of the present invention hasa structure that includes a reflecting plate 267 adjacent to sealant330. Reflecting plate 267 and sealant 330 are disposed in theencapsulation portion region of the electro luminescent display. Sealant330 permanently binds the upper substrate 320 to the lower substrate200.

[0072] Referring to FIGS. 7 and 8, a method for fabricating the organicelectro luminescent display having the reflecting plate 267 in theencapsulating junction region will now be described. Referring to FIG.7, a buffer layer 210 is formed on the lower insulating substrate 200 toprevent impurities such as metal ions diffused from the lower insulatingsubstrate 200 from penetrating to an active layer. After forming thebuffer layer 210, amorphous silicon is deposited and crystallized on thebuffer layer 210 to form a polycrystalline silicon layer, which is thenpatterned to form the active layer 220. A gate insulating layer 230 isdeposited on all surfaces of the lower insulating substrate 200containing the active layer, and gate metal is deposited and patternedon the gate insulating layer to form a gate electrode 240.

[0073] After forming the gate electrode 240, an impurity having apredetermined conductive type is doped in the active layer by using thegate electrode 240 as a mask to form source/drain regions 221 and 225. Aregion with no impurity doped between the source region 221 and thedrain region 225 acts as a channel region 223. After forming thesource/drain regions 221 and 225 on the active layer 220, an interlayerinsulating layer 250 is formed over the entire surface of the lowerinsulating substrate 200, and contact holes 251 and 255 are formed toexpose some portions of the source/drain regions 221 and 225 on theinterlayer insulating layer 250.

[0074] After depositing a conductive material on the interlayerinsulating layer 250 including the contact holes 251 and 255, theconductive material is patterned to form source/drain electrodes 261 and265 connected to the source/drain regions 221 and 225 through thecontact holes, thereby forming a TFT (T) consisted of the active layer220, a gate electrode 240, and the source/drain electrodes 261 and 265,etc.

[0075] In this case, when the source/drain electrodes 261 and 265 areformed, a reflecting plate 267 of a metal thin layer consisted of theconductive material is also formed in the encapsulating junction regionof the lower insulating substrate 200 at the same time. A metal having agood reflectivity is used for the conductive material, and generally Al,Cr, Mo, W, Ti, Ta, or alloy thereof is used for the same. After formingthe reflecting plate 267 of the encapsulating junction region and thesource/drain electrodes 261 and 265, a passivation layer 270 isdeposited on the lower insulating substrate 200, and a via-hole 275 isformed on the passivation layer 270 to expose some portions of one ofthe source electrode 261 and the drain electrode 265, for example, someportions of the drain electrode 265.

[0076] After depositing a lower electrode material on the passivationlayer 270 including the via-hole 275, the lower electrode is patternedto form a lower electrode 280 electrically connected to the drainelectrode 265 through the via-hole 275. After forming the lowerelectrode 280, a pixel defining layer 290 is deposited on the entiresurface of the lower insulating substrate 200 and patterned to form anopening portion 295 that exposes some portions of the lower electrode280.

[0077] An organic layer 300 is then formed on the pixel defined layer290 including the opening portion 295. And an upper electrode 310 isformed on the organic layer 300 over the entire surface of the lowerinsulating substrate 200 to form a light emitting element (LE) made upof the lower electrode 280, organic layer 300, and the upper electrode310. The lower insulating substrate 200 is then encapsulated to theupper substrate 320 by using a sealant 330 in the encapsulating junctionregion.

[0078] The sealant 330 is preferably a light-curing sealant, and morepreferably a light curing sealant capable of being cured not only byexposure to light in an ultraviolet range but also to light in thevisible range. 30Y-296G (three bond), XNR5516 (Nagase Ciba),electrolyte, or Kyoritsu are preferably used for the sealant 330.

[0079] In addition, the thickness “L” in FIG. 8 of the sealant 330 is adistance between the reflecting plate 267 and the upper substrate 320.This thickness L is preferably set to cause constructive interference inthe light used to cure the sealant 330. Constructive interference is tooccur between the incident light and the light reflected off thereflecting plate 267. The optimal distance L between the reflectingplate and the opposite substrate can be determined by the followingequation:

L=λ/4+(n−1)λ/2(n=1, 2, 3, . . . )

[0080] And ultraviolet rays or visible rays are then irradiated on theupper substrate 320 to cure the sealant 330. The optimal range forwavelength used to cure the sealant is from 200 nm to 700 nm. Anotherdesign consideration is that it is preferable to have at least 25% ofthe total surface area of the sealant 330 in contact with reflectingplate 267. As discussed earlier, it is preferable to form the reflectingplate 267 and the source/drain electrodes 261 and 265 at the same timeto reduce the number of processing steps and to reduce manufacturingcosts in the fourth embodiment. Alternatively, the reflecting plate 267can be deposited and patterned at the same time as when the gateelectrode 240 is formed. Alternatively, the reflecting plate 267 can beformed at the beginning of the process, before buffer layer 210 isformed on lower insulating substrate 200. Before forming the bufferlayer 210, a material having good reflectivity, such as any one metal ofAl, Mo, Ti, Ag and Mg, or an alloy containing at least one of thesemetals (i.e., Mo/Al/Mo, Ti/Al/Ti) may be deposited and patterned on thelower insulating substrate 200 to form the reflecting plate 267 in theencapsulating junction region of the display.

[0081] In another design consideration, the width of the reflectingplate 267 in FIG. 8 is illustrated to be larger than the contact area ofthe sealant 330, however, the width of the reflecting plate 267 may beformed to be smaller than the contact area contact area of the sealant330. In such a scenario, the sealant 330 may contact lower insulatingsubstrate 200.

[0082] The inclusion of the reflecting plate 267 in the design of theelectro luminescent display attached to a light-cured sealant 330 in theedge or encapsulation junction region is advantageous for the followingreason. Light used to cure the sealant 330 also exposes other portionsof the electro luminescent display. This light used to cure the sealant330 can damage other parts of the electro luminescent display. Byplacing a reflective plate in the encapsulation junction region of thedisplay, less incident light energy is needed to cure the sealantbecause both the incident light and the reflected light can be used tocure the sealant. Therefore, the intensity of the incident light neededto cure the sealant is less if the reflecting plate is present.Therefore, because less incident light is needed to cure the sealant,less damage is sustained by the electro luminescent display during thecuring process.

[0083] Turning now to FIGS. 9 and 10, FIGS. 9 and 10 illustrate topviews of electro luminescent displays according to the fourth embodimentof the present invention. As is clearly illustrated in FIGS. 9 and 10,the width of the sealant 330 is greater than the width of the reflectingplate 267. Therefore, in the designs illustrated in FIGS. 9 and 10, thesealant 330 may be in contact with lower insulating substrate 200.

[0084] In FIG. 9, the reflecting plate 267 is formed as one continuouspiece in the form of a closed square. Alternatively, in FIG. 10, thereflecting plate 267 is formed of four discrete portions disconnectedfrom each other. It is to be appreciated that the reflecting plate 267does not serve to conduct electricity, and thus having four discretesegments in FIG. 10 works just as well as one continuous closed piece inFIG. 9.

[0085] Fifth Embodiment

[0086]FIG. 11 is a cross-sectional view showing the encapsulatingjunction region of the organic electro luminescent display in accordancewith a fifth embodiment of the invention. The organic electroluminescent display according to the fifth embodiment has a similarstructure as that of the fourth embodiment except the location of thereflecting plate 267. The reflecting plate 267 in the fifth embodimentof the present invention is in an inside surface of upper substrate 320instead of being on the inside surface of lower insulating substrate200. In order to form the structure of FIG. 11, after forming the TFTand the light emitting element LE on the lower insulating substrate 200as illustrated in FIG. 7, a metal thin layer is then deposited andpatterned on the inner side of the upper substrate 320 to form thereflecting plate 267 in the encapsulating junction region. As in thefourth embodiment, the upper substrate 320 is bonded to the lowerinsulating substrate 200 by using the sealant 330 in the encapsulatingjunction region.

[0087] Sixth Embodiment

[0088]FIG. 12 is a cross sectional view showing an encapsulatingjunction region of the organic electro luminescent display in accordancewith a sixth embodiment of the invention. The organic electroluminescent display according to the sixth embodiment has a similarstructure as that of the fourth and fifth embodiments except for thelocation of the reflecting plate 267. In the sixth embodiment, thereflecting plate 267 is located on the outer side of lower insulatingplate 200. In the sixth embodiment as in the fourth and the fifthembodiments, the reflecting plate is located only in the encapsulatedjunction region at the edges of the electro luminescent display.

[0089] In order to make the structure of FIG. 12, after forming the TFTand the light emitting element on the lower insulating substrate 200 asillustrated in FIG. 7, the upper substrate 320 is bonded to the lowerinsulating substrate 200 by using the sealant 330 in the encapsulatingjunction region. After encapsulating the upper substrate 320 to thelower insulating substrate 200, a metal thin layer is deposited andpatterned on an outer side of the lower insulating substrate 200 to formthe reflecting plate 267 in the encapsulating junction region.

[0090] Seventh Embodiment

[0091]FIG. 13 is a cross sectional view showing an encapsulatingjunction region of the organic electro luminescent display in accordancewith a seventh embodiment of the invention. The organic electroluminescent display according to the seventh embodiment has a similarstructure as that of the fourth embodiment but that the reflecting plate267 is formed on an outer side of the upper insulating plate 320 asopposed to an inner side of lower insulating substrate 200.

[0092] In order to form the structure of FIG. 13, after forming the TFTand the light emitting element on the lower insulating substrate 200 asillustrated in FIG. 7, a thin metal layer is deposited and patterned onthe outer side of the upper substrate 320 to form the reflecting plate267 in the encapsulating junction region. After forming the reflectingplate 267 in the encapsulating junction region on the outer side of theupper substrate 320, the upper substrate 320 is then bonded to the lowerinsulating substrate 200 by using the sealant 330 in the encapsulatingjunction region.

[0093] Eighth Embodiment

[0094]FIG. 14A and FIG. 14B are a cross sectional view showing anencapsulating junction region of the organic electro luminescent displayin accordance with an eighth embodiment of the invention. The organicelectro luminescent display according to the eighth embodiment has asimilar structure as that of the fourth embodiment except that awaveguide 217 is formed on the inner side of lower insulating substrateinstead of the reflecting plate 267. Preferably the wave guide isunevenness or a convex lens. FIG. 14A illustrates the wave guide 217 asunevenness. FIG. 14B illustrates wave guide 217 as a convex lens.

[0095] Referring to FIG. 14A and FIG. 14B, the wave guide 217 of theorganic electro luminescent display according to the eighth embodimentis formed on the inner side of the encapsulating junction region of thelower insulating substrate 200 during the process of forming the TFThaving the structure illustrated in FIG. 7 in the pixel portion. Afterdepositing and patterning the buffer layer 210, the wave guide 217 isformed in a position corresponding to the encapsulating junction regionof the lower insulating substrate 200.

[0096] Alternatively, the wave guide 217 may be formed simultaneous tothe patterning the gate insulating layer 230 and after depositing thegate insulating layer 230. Alternatively, wave guide 217 can be formedsimultaneous to the etching of the interlayer insulating layer 250 toform the contact holes 251 and 255. Alternatively, the wave guide 217may be formed simultaneous to the etching of the passivation layer 270to form the via-hole 275.

[0097] Another alternative is to form a multi-layered wave guide 217that is formed simultaneous to the formation of the buffer layer 210,gate insulating layer 230, interlayer insulating layer 250, andpassivation layer 270. Alternatively, wave guide 217 made out ofmaterial having the optical transmissivity may be formed in a separateprocess step separate from the process of forming the other layers inFIG. 7.

[0098] The wave guide 217 is formed by adjusting an angle inconsideration of a refraction index of the incident light, and makes theincident light focused on the sealant 330 of the encapsulating junctionregion to be formed later by the refraction.

[0099] Ninth Embodiment

[0100]FIG. 15A and FIG. 15B are a cross-sectional view showing anencapsulating junction region of the organic electro luminescent displayin accordance with a ninth embodiment of the invention. The organicelectro luminescent display according to the ninth embodiment has thesame structure in the pixel portion as that of the eighth embodimentexcept that the wave guide 217 is formed on an inner surface of theupper substrate 320 instead of on the inner surface of the lowerinsulating substrate. FIG. 15A illustrates wave guide 217 as unevennessand FIG. 15B illustrates wave guide 217 as a convex lens.

[0101] The method of forming the structure if FIG. 15A and FIG. 15B isas follows. After forming the TFT and the light emitting element on thelower insulating substrate 200, a material having optical transmissivityis deposited on the inner side of the upper substrate 320. The materialhaving the optical transmissivity is then patterned to form the waveguide 217 on the inner of the upper substrate 320 in the encapsulationjunction region. After forming the wave guide 217 on the inner side ofthe encapsulating junction region in the upper substrate 320, the lowerelectrode 280, the organic layer 300, and the upper electrode 310 arethen formed on the upper substrate 320.

[0102] Tenth Embodiment

[0103]FIG. 16A and FIG. 16B are a cross-sectional view illustrating anencapsulating junction region of the organic electro luminescent displayin accordance with a tenth embodiment of the invention. The organicelectro luminescent display according to the tenth embodiment has theTFT and the light emitting element shown in FIG. 7 in the pixel portion,and has two wave guides 217, one formed on the inner surface of theupper substrate 320 and one formed on the inner surface of the lowerinsulating substrate 200. FIG. 16A illustrates wave guide 217 asunevenness while FIG. 16B illustrates wave guide 217 as a convex lens.

[0104] The wave guide 217 is formed on the inner side lower insulatingsubstrate 200 is formed according to the same processes as thatdescribed in the eighth embodiment of FIG. 14A and FIG. 14B. The waveguide 217 formed on the inner side upper substrate 320 is made accordingto a process described in the formation of the wave guide 217 in thediscussion of FIGS. 15A and 15B (the ninth embodiment). That is, thelower electrode 280, the organic layer 300, and the upper electrode 310are then formed on an inner surface of upper substrate 320 afterwaveguide 217 is formed in the inner surface of upper substrate 320.

[0105] In addition, in the above-mentioned embodiments of the invention,an organic electro luminescent display having enhanced curing efficiencyis disclosed by using both a reflecting plate and a wave guide formed inthe upper substrate 320 or the lower insulating substrate 200 eitherrespectively or anti respectively. Alternatively, two reflecting platesmay be used, one attached to a surface of the upper substrate 320 andone attached to a surface of lower insulating substrate 200. Thereflecting plates formed on both sides of the organic electroluminescent display are preferably formed to have a mirror attached to.

[0106] According to the invention, auxiliary layers are formed to removeorganic layers on the encapsulating junction region, so that theinvention can provide an organic electro luminescent display capable ofeasily removing the organic layers formed on the encapsulating junctionregion during the process of forming organic layers. In addition, theinvention can provide a method for fabricating the organic electroluminescent display with reduced damage in the pixel portion by removingthe organic layers disposed on auxiliary layers by a laser instead ofremoving the organic layers directly formed on the substrate.

[0107] Furthermore, according to the invention, a reflecting plate isdisposed in the encapsulating junction region, so that the light emittedfrom the light source is reflected by the reflecting plate for curingthe sealant, thereby enhancing the curing state of the sealant andputting the encapsulation of the substrates in better condition. Inaddition, with the reflective plate, the curing time is reduced,resulting in less damage sustained in the pixel regions of the display.

[0108] While the invention has been described with reference to aparticular embodiment, it is understood that the disclosure has beenmade for purpose of illustrating the invention by way of examples and isnot limited to limit the scope of the invention. And one skilled in theart can make amend and change the invention without departing from thescope and spirit of the invention.

What is claimed is:
 1. An organic electro luminescent display,comprising: a first electrode formed on a lower insulating substrate;auxiliary layers formed on edge portions of the lower insulatingsubstrate away from portions of the lower insulating substrate where thefirst electrode is form; a pixel defining layer arranged to cover only afraction of an upper surface of the first electrode; an organic layerarranged over exposed portions of the upper surface of the firstelectrode, over the pixel defining layer and not over the auxiliarylayers; a second electrode formed on the organic layer; and an uppersubstrate arranged to encapsulate the first electrode, the organiclayer, and the second electrode.
 2. The display of claim 1, wherein theauxiliary layers serve to aid in a removal of portions of the organiclayer formed over the auxiliary layers in the edge portions of thedisplay.
 3. The display of claim 1, wherein the auxiliary layerscomprise a material being selected from the group consisting of ITO, IZOand ICO.
 4. The display of claim 1, the auxiliary layers being comprisedof a material selected from the group consisting of acrylic photoresistand polyimide, the pixel defining layer being comprised of the samematerial that the auxiliary layers are comprised of.
 5. The display ofclaim 1, the auxiliary layers being comprised of a material having anabsorption rate that is higher than an absorption rate of the organiclayer at a wavelength used to remove the organic layer from theauxiliary layers.
 6. The display of claim 1, the auxiliary layers beingcomprised of materials that require a higher laser energy density toremove than the organic layer.
 7. A method for fabricating an organicelectro luminescent display, comprising: forming a first electrode on alower insulating substrate; forming a pixel defining layer on onlyportions of the first electrode leaving portions of the first electrodeexposed; forming auxiliary layers on the lower insulating substrate on acathode contact and an encapsulating junction region of the lowerinsulating substrate outside a pixel region; forming an organic layer onthe pixel defining layer, the exposed portions of the first electrodeand on the auxiliary layers; removing portions of the organic layerarranged on the auxiliary layers; forming a second electrode onremaining portions of the organic layer; and encapsulating the firstelectrode, the organic layer, and the second electrode by an uppersubstrate.
 8. The method of claim 7, the auxiliary layers facilitate inthe removal of portions of the organic layer arranged on top of theauxiliary layers.
 9. The method of claim 7, the auxiliary layers beingcomprised of a material selected from the group consisting of ITO, IZOand ICO, the auxiliary layers being formed simultaneous to the formationof the first electrode.
 10. The method of claim 7, the auxiliary layersbeing comprised of a material selected from the group consisting ofacrylic photoresist and polyimide, the auxiliary layers being formedsimultaneous to the formation of pixel defining layer.
 11. The method ofclaim 7, the auxiliary layers being comprised of a material having ahigher absorption rate at the wavelength used to remove the organiclayer from the auxiliary layers than the absorption rate of the organiclayer.
 12. The method of claim 7, the auxiliary layers being comprisedof a material that requires a higher laser energy density for removalthan the energy density needed to remove the organic layer.
 13. Themethod of claim 7, wherein the step of removing the organic layer uses alaser for the removal of the organic layers disposed on the auxiliarylayers.
 14. The method of claim 13, wherein an energy intensity of thelaser for removal of the organic layer disposed on the auxiliary layersis at least 50 mJ/cm².
 15. The method of claim 14, wherein an energyintensity of the laser for removal of the organic layer disposed on theauxiliary layers is at least 125 mJ/cm².
 16. An organic electroluminescent display, comprising: a lower insulating substrate on whichTFTs and light emitting elements are formed; an upper substrate attachedto the lower insulating substrate; an encapsulating junction regionadapted to encapsulate and attach the upper substrate to the lowerinsulating substrate via a sealant; and a reflecting plate arranged inthe encapsulating junction region at any one side of the upper substrateand the lower insulating substrate.
 17. The display of claim 16, thereflecting plate being formed on an inner side of one of the uppersubstrate and the lower insulating substrate, the reflecting platefacing the other of the upper substrate and the lower insulatingsubstrate.
 18. The display of claim 16, the reflecting plate beingformed on an outer side of one of the upper substrate and the lowerinsulating substrate.
 19. The display of claim 16, the sealant being anoptical curing sealant.
 20. The display of claim 19, the sealant beingan optical curable sealant cured by exposure to light in either avisible ray range or an ultraviolet ray range.
 21. The display of claim16, the reflecting plate comprising a metal thin layer deposited on anyone side of the upper substrate and the lower insulating substrate. 22.The display of claim 16, the reflecting plate comprising a mirrorattached to the outer side of one of the upper substrate and the lowerinsulating substrate.
 23. The display of claim 16, wherein a distancefrom the reflecting plate to a nearest surface of a substrate opposingthe reflecting plate is designed so that curing light reflected off thereflective plate constructively interferes with curing light incident tothe reflective plate.
 24. An organic electro luminescent display,comprising: a lower insulating substrate on which TFTs and lightemitting elements are formed; an upper substrate bound to the lowerinsulating substrate; an encapsulating junction region adapted toencapsulate the upper substrate to the lower insulating substrate via asealant; and a wave guide arranged in the encapsulating junction regionon an inner side of one or both of the upper substrate and the lowerinsulating substrate.
 25. The display of claim 24, wherein the waveguide is unevenness.
 26. The display of claim 24, wherein the wave guideis a convex lens.
 27. The display of claim 24, wherein the wave guide isformed on both the upper substrate and the lower insulating substrate.28. The display of claim 24, wherein the encapsulating junction regionbeing separate from where the TFTs and the light emitting elements arearranged.
 29. The display of claim 24, wherein the wave guide iscomprised of a material with optical transmissive property.
 30. Thedisplay of claim 29, wherein the wave guide is comprised of a materialselected from the group consisting of SiO₂ and SiN_(x).
 31. An organicelectro luminescent display, comprising: a lower insulating substrate onwhich a pixel portion is arranged; an upper substrate arranged over thelower insulating substrate; and a sealing material arranged between theupper substrate and the lower insulating substrate and adapted to sealthe upper substrate to the lower insulating substrate, wherein a metallayer is arranged between the lower insulating substrate and the sealingmaterial.
 32. The display of claim 31, wherein the sealing material isformed along the peripheries of the substrates and not in the pixelportion of the display.
 33. The display of claim 32, wherein the metallayer is formed coextensively along with the sealing material and is ofthe shape of a closed polygon.
 34. The display of claim 32, wherein themetal layer is formed discontinuously in separate unconnected piecesaround a perimeter of the display and along the sealing material. 35.The display of claim 31, the metal layer comprising a material beingselected from the group consisting of Al, Mo, Ti, Ag, Mg and an alloycontaining at least one of Al, Mo, Ti, Ag and Mg.
 36. The display ofclaim 31, wherein at least 25% of the total surface area of the sealingmaterial is in contact with said metal layer.
 37. An organic electroluminescent display, comprising: a lower insulating substrate on which apixel portion is formed; an upper substrate arranged on the lowerinsulating substrate; and a sealing material arranged between the uppersubstrate and the lower insulating substrate, the sealing material beingadapted to attach the upper substrate to the lower insulating substrate;and a reflecting plate arranged between the lower insulating substrateand the sealing material.
 38. The display of claim 37, the sealingmaterial being arranged along peripheries of the substrates and outsideof the pixel portion.
 39. The display of claim 38, wherein thereflecting plate is arranged to be coextensive with the sealing materialand is in the shape of a closed polygon.
 40. The display of claim 38,the reflecting plate being a plurality of separate unconnected segmentsarranged essentially along the sealing material.
 41. The display ofclaim 37, wherein at least 25% of an outer surface of the sealingmaterial is in contact with the reflecting plate.
 42. The display ofclaim 37, the reflecting plate being comprised of metal.
 43. The displayof claim 42, the metal being selected from a group consisting of Al, Mo,Ti, Ag, Mg and an alloy containing at least one metal of Al, Mo, Ti, Agand Mg.
 44. An organic electro luminescent display, comprising: a lowerinsulating substrate on which TFTs and light emitting elements areformed; an upper substrate bound to the lower insulating substrate; anencapsulating junction region surrounding and outside of the TFTs andlight emitting elements, the encapsulating junction region adapted toattach the upper substrate to the lower insulating substrate via asealant; and an auxiliary layer disposed in the encapsulating junctionregion of the display.
 45. The display of claim 44, wherein theauxiliary layer is arranged on a layer being selected from the groupconsisting of the upper substrate and the lower insulating substrate.46. The display of claim 44, wherein the auxiliary layer is arranged onan outer side of one of the upper substrate and the lower insulatingsubstrate.
 47. The display of claim 44, wherein the auxiliary layers arereflecting plates.
 48. The organic electro luminescent display accordingto claim 44, wherein the auxiliary layers are adapted to aid in removalby laser of organic layers deposited on the auxiliary layers.